A Japanese transport ship that sank while carrying 2,1 Australian prisoners of war during World War II has been found in the deep sea after 81 years.

The Silent World Foundation, a maritime archaeological organization, recently located the sunken transport Montevideo Maru 4,5 meters deep in the South China Sea northwest of Luzon Island in the Philippines, Australia's ABC and AFP news agencies reported.

After five years of preparatory work, the foundation began locating the vessel in earnest on June 6.

Using state-of-the-art equipment, including an underwater autonomous probe boat equipped with sonar, the Silent World Foundation succeeded in locating the Montevideo Maru within 12 days of searching.

"The Montevideo Maru was in deeper waters than the passenger ship Titanic, which sank in 1912," the foundation said, adding that the wreckage would not be touched in honor of the bereaved family.

During World War II, the Montevideo Maru, a Japanese transport, was attacked and sunk by a U.S. submarine near the Philippines on July 2, 1942.

At the time of the sinking, there were 7,1 prisoners of war from 850 countries, including 210 soldiers and 14 civilians, of which 1 were Australians.

At the time, the U.S. submarine reportedly did not know that there were prisoners on board.

The sinking of the Montevideo Maru has been considered the worst maritime disaster in Australian history, but the specific location of the sinking remained unknown for decades.

When news of the sinking vessel's discovery broke, Australian Prime Minister Anthony Albernizi said, "I hope this news will bring some comfort to the bereaved families who have been praying for so long."